NET cancer: the stealthy killer

Neuroendocrine Tumours (NETs) is an increasingly common, yet poorly understood group of cancers. Though early detection is crucial, NET cancer often remains undiagnosed for years.

Neuroendocrine Tumours (NETs) is an increasingly common, yet poorly understood group of cancers. Early diagnosis radically improves a patient's prospects, but these stealthy killers often remain undiagnosed for years - only being identified once they have reached an advanced stage and survival rates have been drastically reduced.

NET cancers are very difficult to detect and the typical delay in diagnosis of between five and seven years often gives the tumours the opportunity to metastasize (spread), making most of them incurable.

According to recent studies, around 1 in every 20 000 people will develop some form of NET. Despite this, many medical professionals have little or no experience with this group of cancers. The incidence of NETs is also rising dramatically. It has increased more than a 5-fold in the last 30 years and is predicted to continue to do so.

The need for better awareness and understanding of NET cancers is underscored by the coverage of the recent death of Steve Jobs, former Apple CEO. Jobs had a pancreatic neuroendocrine tumour (pNET), a slow growing and rare cancer that is often confused with the more aggressive pancreatic cancer, which many reports said he had.

“Neuroendocrine tumours are becoming increasingly common,” confirms Professor Jose M Ramos of the Wits University Donald Gordon Medical Centre, “both due to a true increase in incidence and also because of improved diagnosis. Incidence rates in the USA, for instance, have risen from 1.1 cases per 100 000 in the 1970s to between 5.6 and 6.2 cases today. Unfortunately, we don’t have reliable statistics for South Africa, but we can assume the rates are similar here.”

What are NETs?

Neuroendocrine tumours are a group of unusual, often slow-growing cancers, which are believed to originate from neuroendocrine cells found throughout the body. There are many types that can occur, although most are found in the gastrointestinal tract, pancreas and lungs. “Around 60% of NETs occur in the gastrointestinal tract,” affirms Professor Ramos, “27% in the lungs, and the rest in other sites, such as the ovaries, testes, breasts and prostate.”

Neuroendocrine cells are found in the respiratory and digestive tracts, and the endocrine glands, such as the adrenal, pancreas, thyroid and pituitary glands. NET cancers develop when these specialised cells begin to divide uncontrollably and grow into an abnormal tissue mass or tumour.

What causes NETs to form?

How NETs are formed is still not fully understood. “As is true for many cancers, we know quite a bit about their behaviour once they have occurred, but not why they occur,” observes Professor Ramos. “While there a few cases where the risk of developing multiple NETs appears to be part of a specific familial syndrome, no explicit risk factors for this group of cancers has been identified yet.”

Why are NETs so difficult to diagnosis?

“NETs are difficult to detect and diagnose accurately for several reasons,” explains Professor Ramos. “It may be because the tumours are not triggering symptoms or causing the patient problems — as NETS are often slow-growing and asymptomatic until late in the disease. Moreover, the primary tumours may remain small and only cause issues once the tumours have metastasized and spread.”

Professor Ramos identifies the diverse behaviour of NETs as another diagnostic difficulty. “The behaviour of NETs can vary from very indolent to extremely aggressive,” he notes. “Modern pathology has the ability to accurately diagnose the majority of these tumours due to the availability of specific ‘markers’, but, if these markers are not used, a NET may be incorrectly diagnosed as another type of tumour.”

The third reason Professor Ramos cites is the fact that the symptoms are very often similar to other, more common conditions: “If symptoms are present, they range from tiredness and digestive complaints to abdominal pain, flushing, diarrhoea and palpitations, symptoms that can be easily misdiagnosed as allergies, anxiety, asthma, panic attacks, irritable bowel syndrome or menopause.”

This was certainly true in the case of Johan Petrus van den Berg, who lived with the symptoms of his tumour for 10 years before it was correctly diagnosed. “I used to suffer hot, blotchy flushes and red eyes,” he explains, “which was originally diagnosed as a skin condition, and then an allergic reaction. It was only by chance, when I went to pick up my wife’s medication and the doctor was startled by how serious my symptoms were at that exact moment, that I was referred to specialists and, eventually, diagnosed with carcinoid syndrome.”

“The fact that many of these tumours lack specific symptoms does make it difficult,” agrees Professor Ramos, “but problems such as unexplained weight loss, persistent or recurrent abdominal pain, flushing, diarrhoea, palpitations or low blood sugar should be investigated further. While it must be stressed that these symptoms are common and seldom point to the presence of NETs, it is incumbent on clinicians to be aware of, and to consider, this group of cancers when dealing with patients with persistent, unexplained problems like these.”

New treatments offer hope

The treatment of a NET cancer depends on the size and location of the tumour, whether the cancer has metastasized or spread, and the patient’s overall health. There are a variety of treatment options available, including surgery, somatostatin analogs (hormone injections), hepatic artery embolization or HAE (if the tumour has spread to the liver), chemotherapy and radionuclide therapy (hormone-delivered radiotherapy)5.

“The last few years have been very exciting and rewarding in terms of how we are able to manage and treat NETs,” enthuses Professor Ramos. “Many different treatment options now exist, including new surgeries, targeted drugs, hormone blockers and targeted radiation therapy. These have enabled us to better treat symptoms, as well as prolonging survival in a large percentage of patients.”

There are also blood tests available now that can help medical professionals diagnose NETs. “The tests can definitely aid in the diagnosis of NETs, but, unfortunately, there is no single test that can predictably diagnose these tumours to the extent that it can be used as a screening tool,” the Professor cautions.

Professor Ramos also points out that, while the different treatment options can be used very effectively — usually in combination — to manage the cancer, only surgical resection or removal can cure the patient. “Early tumours can often be cured by surgical resection,” he confirms, “which is why early and accurate diagnosis is so important, but, even if the tumour cannot be cured, prolonged survival, with a good quality of life, is often possible.”

So much so, that Professor Ramos believes patients should adopt an optimistic and hopeful outlook. “A nihilistic attitude, even with seemingly advanced, incurable disease, is not appropriate,” he concludes, “as the numerous different treatment modalities now available present the possibility of years of good-quality, symptom-free survival.”

Ask the Expert

CANSA’s purpose is to lead the fight against cancer in South Africa. Its mission is to be the preferred non-profit organisation that enables research, educates the public and provides support to all people affected by cancer. Questions are answered by CANSA’s Head of Health Professor Michael Herbst and Head of Advocacy Magdalene Seguin. For more information, visit cansa.org.za.

posted on 31-10-2016

posted on 26-10-2016

posted on 26-10-2016

posted on 26-10-2016

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